Repeated removal of blood for therapeutic and research purposes is common in hospitalized adult patients on clinical trials. To ensure the accuracy of these specimens, the removal of discard blood (5 to 10 mL) is standard practice. This discard blood is not typically reinfused because of clinical concerns about clot formation. This discard, or "wasting," of blood is often a concern for patients and health care providers because of the associated blood loss. This study is designed to determine if discard blood from venous access devices is free from clots and suitable for reinfusion. Blood-that is removed for discard before laboratory specimens are obtained was filtered to determine the presence of clots. Half the blood removed as discard from the patient's vascular access device was filtered immediately upon removal to determine the presence of clots. The second half of the discard blood was allowed to dwell in a syringe for 5 minutes and then filtered. The amount of clot present in the two samples was quantified and compared. Discard blood was not reinfused into patients in this study. Fifty vascular access devices were evaluate(L Formed clots were found in 24 of the 50 immediately filtered discard specimens, while clots were found in only 2 of 50 specimens allowed to dwell for 5 minutes. The clinical significance of these findings includes careful consideration of the potential risks of reinfusing discard blood containing clots. In light of the study findings, routine reinfusion of discard blood in adult oncology patients should be avoided.